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Utilization :: –the percentage of time a device is busy servicing a “customer”. Throughput :: –the number of jobs processed by the “system” per unit time. Response time :: – the time required to receive a response to a request (round-trip time (RTT) ). Delay :: –the time to traverse from one end to the other of a system. Generic Performance Metrics Computer Networks Performance Metrics 7

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End-to-end Packet Delay End-to-end packet delay :: the time to deliver a packet from source to destination Host (or node). {Most often, we are interested in the packet delay within the communications subnet.} This delay is the sum of the delays on each subnet link traversed by the packet. Each link delay consists of four components[B&G Bertsekas and Gallager]: Computer Networks Performance Metrics 16

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Link Packet Delay 1. The processing delay [PROC] between the time the packet is correctly received at the head node of the incoming link and the time the packet is assigned to an outgoing link queue for transmission. 2. The queuing delay [QUEUE] between the time the packet is assigned to a queue for transmission and the time it starts being transmitted. During this time, the packet waits while other packets in the transmission queue are transmitted. Computer Networks Performance Metrics 17

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Link Packet Delay 3. The transmission delay [TRANS] between the times that the first and last bits of the packet are transmitted. 4. The propagation delay [PROP] is between the time the last bit is transmitted at the head node of the link queue and the time the last bit is received at the next router. This is proportional to the physical distance between transmitter and receiver. Computer Networks Performance Metrics 18